The Bridesmaid

From the Book Jacket:
Philip Wardman is an ordinary young man, quiet and good looking, working at an ordinary job, living in an ordinary suburb of London. His one eccentricity is his neurotic fear of violence and death; his ideal of beauty is a statue of a minor Greek goddess, Flora, which stands in his widowed mother's garden. When she gives it away to a friend he impulsively and surreptitiously retrieves it, at the risk of arrest.
At his sister's wedding Philip encounters the living incarnation of the marble Flora: Senta Pelham, a lovely, ethereal actress who disregards conventional morality. She
comes to him that night, coolly informing him that he is the man she has been seeking all her life. A strange and passionate love affair begins.
But darker forces soon intrude. Unlike Philip, Senta is fascinated with death; her disdain for the common run of humanity leads her to propose an evil game: Philip must prove his love for her--by committing murder